This invention is directed to a new low molecular weight copolymer (The PIB/UAR copolymer) that may be prepared by reacting a low molecular weight polyisobutene (PIB) having less than about 32 carbon atoms with an unsaturated acidic reagent in the presence of a free radical initiator. No chain transfer agent is required to prepare the low molecular weight PIB/UAR copolymer. The PIB/UAR copolymer may be useful as is, or as an intermediate for (1) polysuccinimides, (2) detergents or dispersants for lube oil or fuels, (3) pour point depressants and (4) surface sizing agents for paper. The PIB/UAR copolymer may be used by itself or as the ester, amide, imide or metal salt derivative of the PIB/UAR copolymer. Preferred PIB/UAR copolymers are liquid at ambient temperature.
It is known that olefin/unsaturated acidic reagent copolymer compositions may be prepared by reacting an alpha olefin with an unsaturated acidic reagent in the presence of a free radical initiator. This reaction is typically carried out at elevated temperatures either neat or in a solvent or diluent. When the reaction is carried out neat, the resultant copolymers have a high degree of polymerization, which results in a high carbon number and a high molecular weight.
Traditionally, if a lower degree of polymerization, lower carbon number or low molecular weight for a copolymer was desired; it was necessary to use a chain transfer agent during the copolymer preparation to promote chain transfer. This is because the chain transfer agent causes such copolymers to have a lower degree of polymerization, which results in a lower carbon number and a lower molecular weight.
A high temperature of reaction may be used alone or in combination with chain transfer agents to encourage a low degree of polymerization and the resulting low carbon number and low molecular weight. Traditionally, the key factors used to influence the degree of polymerization for a copolymerization reaction were combining high temperature and particular chain transfer agents selected for the degree of polymerization they impart.
One draw back to using an alpha olefin to prepare the copolymer is that the resulting copolymer is typically a glassy solid. A solid copolymer is undesirable because a solid copolymer cannot be handled easily or pumped readily at ambient temperatures. Before further processing, a solid copolymer has to be brought to a consistency that may be pumped readily. This may be accomplished by heating the solid copolymer to a temperature above the melting point or using a solvent to dissolve it. Heating the copolymer is often costly, and the addition of a solvent is often not practical. This is because it is desirable to remove the solvent before the copolymer can be used, and the solvent has to be disposed of in a manner consistent with environmental regulations.
The PIB/UAR copolymer is an improvement over alpha olefin copolymers in two respects. Surprisingly, a chain transfer agent is not required to prepare the PIB/UAR copolymer at the desired low molecular weight. Further, since the PIB/UAR copolymer is liquid, it is not necessary to dissolve the PIB/UAR copolymer by using additional heat or adding solvent before the PIB/UAR copolymer is used. Since no solvent is required, the step of removing the solvent is not necessary either.
Preparing a polysuccinimide by reacting a PIB/UAR copolymer with a polyamine and an alkenyl or alkyl succinic acid derivative offers several advantages over preparing a polysuccinimide by reacting alpha olefin prepared copolymers with polyamines and alkenyl or alkyl succinic acid derivative. These advantages include: (1) no chain transfer agent is required to produce the PIB/UAR copolymer having the desired low molecular weight, and (2) since the PIB/UAR copolymer is liquid, it does not require melting or the addition of a solvent before it can be used to make a polysuccinimide and (3) since solvent is not required, the solvent does not have to be removed thus eliminating handling or disposal cost.